Underverse is a Webcomic-turned Web Animation based off of the video game Undertale and a Tumblr webcomic named X-Tale created by Jael Peñaloza (a.k.a. Jakei). Though the series started as a Web Comic with Sans and Ink Sans going after XTale Chara/Cross after they take half of Sans' soul to sustain themselves, things just started spiraling from there.

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Underverse provides examples of:

• All According to Plan: In 0.5, according to XGaster, every single action Sans, Frisk and Chara take contributes to his plans in some fashion.
• Allergic to Evil: Dream, since he can only use his powers in a positive environment.
• All for Nothing: Cross and X-Event Chara's attempt to fix their world and make it their own fails spectacularly. Not only does the quarantine on all the Universes they've been in undo everything they've stolen, but Ink brings back XGaster, who takes back the other half of his soul and puts X-Event Chara back in his place. And then XGaster revives the XTale characters as his brainwashed minions, with Chara only keeping his free will because XGaster enjoys his suffering.
• All There in the Manual:
  • A good amount of the more complicated parts of the plot require that you've read the prequel comic beforehand. Likewise, some of the characters' personalities and alignments make more sense if you read about them and their respective Universes.
  • Many aspects about the personalities and lives of the XTale cast - like Cross' extreme phobia of cows - are only available through posts and mini comics in Jakei's Tumblr account.
• Alternate Self: In season 1 alone there are eight different versions of Sans running around, and that's excluding the ones who just happen to look like him.
  Sans (thinking): (Seriously, all those alternate versions of myself will leave me with side effects for life.)
• Alternate Universe: The basis of the Underverse series. The heroes are tasked with trying to stop Cross from carrying out his plan to steal parts of multiple Universes in order to mend his own lost world. X-Event Chara's goal is to get the other half of his father's soul in order to get his world back and punish Ink for allowing XGaster to experiment on X-Event Chara and his brother, even if it means hurting innocent people and destroying other timelines in the process.
  • XGaster's goal is to do what X-Event Chara and Cross were doing, making one world with the best of the others. How he plans to go about it involves destroying all universes except the main universe, Mettaton spreading some sort of wave turning everything black and purple, kidnapping the "player" and corrupting a lot of civilians.
• Amazing Technicolor Battlefield: Dear god, this series has a lot of colors in its fight scenes. 0.4's fight is especially colorful and breathtaking to watch.
• And I Must Scream: In 0.5, a Freeze-Frame Bonus (and decent eyesight) reveal that the people of XTale are still conscious and feel guilty for their actions. XMettaton and XMuffet ask for forgiveness and beg for help respectively, but their words are overpowered by XGaster.
• Anti-Villain: Cross, who only wants to restore his world.
• Anyone Can Die:
  • In Underverse 0.3, Underswap Papyrus and Underswap Chara die, with the former's death happening onscreen in 0.4.
  • By the end of 0.4, the list of confirmed deaths is Underswap Sans, Underfell Sans, Outertale Sans, everyone else from all three of their respective timelines, and the Doodle Sphere (which was said to be the entire Multiverse minus the main Universe). X-Event Chara and Cross also die, but XGaster gives X-Event Chara another chance under the conditions that he's well-behaved while reviving Cross separately and offering him a chance to join them before leaving him behind.
  • Toriel is killed by XAsgore at the end of 0.8 Part 1.
• Apocalypse How: The multiverse is annihilated in an instant by Error Sans, who does so to not play along with Ink and XTale Gaster's "game". This is a class X-5 due to the fact that most of the multiverse is gone.
• An Arm and a Leg: In 0.7 Part 2, Fatal Error wraps his strings around Cross' arms, cracking them. Cross lets his arm break off to deliver a sucker punch on Fatal Error. XGaster fixes it after the fight.
• Art Evolution: Overlapping with Animation Evolution. Jakei started the series with somewhat wobbly Thick-Line Animation, but over time it shifter to a smoother and more detailed Animesque style. You can tell when Jakei made something based on how it looks.
• Art Shift: During Cross's talk with Geno, a close-up shot shifts the artstyle to the coloured pencil style of Geno's original comic.
• The Atoner: Heavily implied with Cross in Season 2.
  Cross: None of you will follow my footsteps of hate.
• The Bad Guy Wins: Pretty much a classic staple within this series.
  • The XTALE series has XTale Chara and XTale Frisk attempting to stop XGaster's repeated attempts to create a perfect universe. They fail in the end and XGaster succeeds at getting his chance of obtaining his perfect universe, with catastrophic results.
  • In Underverse 0.0, half of Sans' soul is taken by X-Event Chara and they escape.
  • In Underverse 0.2, despite being beaten back and losing control of Underfell Sans, Cross still manages to escape with Underfell's Snowdin.
  • Underverse 0.3 really gives the cast a beating. Ink starts losing his emotions after X-Event Chara is brought back to life, X-Event Chara escapes with the Underswap cast, and the Underswap timeline is destroyed, with Underswap Papyrus staying behind with Underswap Chara until the very end.
  • The nail in the coffin is Underverse 0.4. A good chunk of the cast is killed, including Underfell Sans and Underswap Sans, XGaster is revived, and the Doodle Sphere is gone, leaving behind a destroyed multiverse without alternate realities and thus leaving Error the "winner" of the truce. Had it not been for the revelation that CORE Frisk managed to save a good amount of people as well as Cross and Dream safely escaping to the Omega Timeline, it could've been worse.
• Attention Whore:
  • Killer Sans calls XGaster a "limelight hogger" after XGaster steps in to save Cross.
  • Error in 0.7 Part 1. He is visibly enraged that even after destroying the multiverse, nobody is paying attention to him; everyone is focused on XGaster's game.
• Bait-and-Switch: Owners starts out with Flowey talking to someone and correctly deducing that they are "not happy with what [they've] done". At first it seems like he's talking to Frisk/Chara after a genocide run - only for the very next few scenes to reveal that it was actually Sans he was talking to and that Sans and Frisk/Chara have teamed up to kill him.
• Back from the Dead:
  • OVERWRITE is powerful enough to bring back one's soul after death, meaning that no matter how the victim is killed, the person who can OVERWRITE can undo it as if it never happened at all.
  • The entire main cast of X-Tale, except XTale Frisk, are brought back in 0.4 thanks to the combined efforts of XGaster and XTale Alphys. XTale Frisk follows suit not long after.
• Badass in Distress:
  • Ink when Nightmare restrains him in 0.3 Part 1.
  • X-Event Chara for the entirety of 0.4.
• Beam-O-War: Underfell Sans (forcefully) ends up having one against Sans, both using their Gaster Blasters.
• The Bet: Error negotiates a deal with Ink for "no more creation, no more destruction", after their whole war in the multiverse. Both of them end up finding ways around it, with Ink aiding XGaster in creating his Universe indirectly while Error steals the souls of the "anomalies" while not actually destroying them. Once Ink truly breaks it by bringing XGaster back, Error retaliates by finally destroying everything in the Doodle Sphere.
• Big Bad: XGaster for XTale and Underverse. His constant overwriting of XTale turns him into an amoral Reality Warper who wishes to bend the entire multiverse to his twisted vision of perfection. He remains out of focus for most of Underverse's first season, allowing multiple antagonists to squabble for his soul until he's finally restored by Ink and he goes on to become the sole Big Bad for the second season.
• Big Bad Ensemble:
  • There's a whole slew of antagonists competing for the Big Bad title in the first season, the most notable being XTale Chara/X-Event Chara, Nightmare Sans, and Error Sans. X-Event Chara and Nightmare form a tenuous Big Bad Duumvirate while Error is looking to wipe out the "anomalies" from the Multiverse, which are the protagonists. It isn't until the season finale where we finally have a solid Big Bad in the form of XGaster, who shows up the entire ensemble to become the main villain of the second season.
  • While Season 2 does see XGaster taking on a more active role, Nightmare is far from out of the picture, and seems to have his own plans for XGaster's "perfect universe".
• Big Bad Wannabe: Cross tries to make himself out as a threat but is forced to rely on more powerful beings who constantly manipulate him for their own ends.
• Bilingual Bonus:
  • In OWNERS, Undertale Gaster calls XGaster's plans a failure in sign language.
  • While a translation is provided, either through proper subtitles or Youtube captions, Xtra Scene 2 is reportedly way funnier if you know Spanish.
• Blood Knight: X-Event Chara. He enjoys fighting the Sanses and approaches their confrontations with sadistic glee. Until he's significantly depowered by Nightmare.
• Bloodless Carnage: Mettaton's death would be far, far more graphic if he wasn't a robot. This doesn't make his dismemberment any less horrific.
• Blue-and-Orange Morality: Word of God says that this us the real reason the series has No Antagonist despite many characters acting like villains in our eyes; since they are from different universes, their moral compass is different from ours.
• Body Horror:
  • XGaster starts melting in XTALE X from overusing Determination, eventually reducing him from a fairly good-looking skeleton to a melting legless demonic mess. His revival in 0.4 stops the melting part, but he still has no legs, replaced with glitches, and he looks more like a clawed fanged demon with a Slasher Smile than a monster.
  • In 0.3 part 2, X-Event Chara turns Underswap Sans and Papyrus into Amalgamates. XTALE 8 reveals that he stole the idea from XGaster.
• Bookends: The first fight in the series, in 0.0, involves Ink splashing Cross with purple paint, talking, and then splashing Cross again, before using the paint as chains. Ink hits Error with purple paint once in 0.4, and then immediately uses it as string to bind Error.
• Brainwashed and Crazy: All characters from XTale except Cross and XChara are being controlled by XGaster after he revives them at the end of 0.4. Later episodes show there's a good amount of And I Must Scream in the situation, as the XTale cast is self-aware to a degree and there's some underlaying text showing their regrets.
• Came Back Wrong: XGaster's revival has him come back looking more monstrous compared to what he looked like in the prequel comics and past X-Tale Timelines, although he eventually pulls himself back mostly into shape, albeit still missing his legs. He's still a far cry from his old self, however.
• The Cameo: An absolutely staggering number of Undertale AU characters appear in 0.6, with Jakei crediting them at the credits and the video description. Justified because most of the episode takes place in the Omega Timeline, and it was previously stated that Core Frisk and Dream went rescuing as many people from the AUs as they could. Clover of Undertale Yellow briefly appears in 0.8 Part 1.
• Canon Foreigner: The 21 Years comic introduces Galett, Muffet's mother. X-Event Frisk created her in secret so XMuffet could have a protector. XGaster is not happy to find out.
• Canon Welding: Being a Mega Crossover between several Undertale Alternate Universes, this was inevitable.
  • 0.3 part 1 makes it clear that the events of Myebi's comic Ink in Underswap did take place in this continuity. This means that the original Inktale is part of Underverse canon.
  • Dreamtale, CORETale and the origin story of Killer Sans are also canon to Underverse, though only the last one is elaborated upon.
  • Underswap Sans and Papyrus's awareness of the multiverse's existence and familiarity with Core Frisk potentially implies that Errortale/The Ask Error blog is also canon to Underverse at least up to the point where the blog stopped updating. Or at least similar events occurred at some point.
  • Epic Sans and Epic Toriel allude to some earlier crossover comics between Underverse and Epictale, and are surprised that Cross doesn't remember them.
  • Averted in general in regards to episode 0.6, as Jakei specifically points out that Underverse is not canon to the AUs of other creators unless they say so.
• Cassandra Truth: X-Event Chara tries to explain on multiple occasions, directly or indirectly, that Ink works for XGaster, but most people seriously doubt him.
• Character Development: Cross goes from basically canon Sans, to more like his Underswap counterpart but less hyper, to Ax-Crazy laughing lunatic with Jade-Colored Glasses with a dash of Well-Intentioned Extremist and Then Let Me Be Evil, to The Atoner. Then again, finding out that your entire existence is being controlled by an insane perfectionist, your best friend trying to kill you, destroying your own world as a means to fix it and then finding out you CAN'T fix it, getting roped into a crowd made of Eviler than Thou, and finally your last friend revealing he was working for the perfectionist guy will do that to a dude. A prominent example is how in XTALE X he insists everyone calls him Sans and not Cross, but in Underverse 0.8 part 1 he flips it around.
• Chekhov's Gun:
  • CORE Frisk's advice on how to beat Cross in Xtra Scene 1 comes in real handy come 0.3 Part 1.
  • The bottle of deluxe ketchup that Frisk gives to Sans in 0.1. In 0.3 Part 2, when he teleports in front of Underswap Papyrus to save him from X-Event Chara, it takes the attack instead, saving his life.
  • The mysterious vial Ink seems keen on protecting and keeping secret, first appearing in 0.3 Part 1. 0.4 reveals it to be half of XGaster's soul, which Ink proceeds to set free, allowing XGaster to come back.
  • The artwork for Fresh's theme ver.3 has a purple gift box in the background. In 0.5, XGaster makes that very same gift box at Ink's request. It also crosses with Foreshadowing, as in XTRA SCENE 2, Fresh says that Ink promised him something nice. In 0.7 Part 1, this becomes the catalyst for Fresh!Ink.
• Clone Angst: Cross and XGaster both express different shades of this: Cross wonders if his life is worth anything considering he is a copy, while XGaster asks Core Frisk who decided he is the fake and that the others are better.
• Color-Coded Time Stop : How XMuffet's time-stops manifest. Everything turns negative except for the unfrozen people.
• The Corruption: The only way to describe how XGaster's code affects his surroundings. Everything he or his puppets attack — buildings, objects, even people — transform into his purple colour pallette, and it's implied that he's somehow affecting their code or something.
• Crazy Consumption: Cross' consumption of the taco Underswap Papyrus offers him.
• Crossover-Exclusive Villain: At first the series features the typical Undertale AU Big Bads of the community (a.k.a. Error and Nightmare), but then they both are upstaged by XGaster, who is original to the series.
• Darker and Edgier: Starting with the ending in Underverse 0.3 Part 1, chaos starts to brew when X-Event Chara is finally revived.
• Dark Is Not Evil: Even though Underfell Sans is very much a Jerkass, he still has good intentions...ish.
• A Death in the Limelight:
  • Outertale Sans appears as Sans is snooping around, but he barely spends any time with him before Killer takes his life.
  • In 0.5, Muffet and Mettaton die at the hands of their XTale counterparts, barely a few minutes after their first appearance.
• Death Seeker: Averted when Sans saves Underswap Papyrus' life by Taking the Bullet.
• Decoy Backstory: When Sans asks Ink where Cross came from, he says that Cross is "from a Genocide timeline with no Reset capabilities", and that he has no idea how his world was erased or how the human who carried it out was sealed in Cross' body. All of this is lies; there was no Genocide run, the world's Reset capabilities were fine, and Ink knows exactly what happened to Cross and the human that led to his world's erasure. He lied to Sans to manipulate him on behalf of the guy who planned the whole thing.
• Deliberately Monochrome: XTale specifically is the Limited Palette version of this trope. The prevalent colours are greyscale and various shades of lilac, to the point even the sky and the plants are lilac. Inexplicably, food maintains its normal colour. The lockets are gold with brown strings, and magic still has the same variety in colour as Undertale. The magic bit gets erased after the destruction of XTale; while Blue Soul Magic remains the same, all other types of magic get changed to that shades of lilac palette. Overall it makes for a stark contrast to all the other AUs in the series, and gets lampshaded when the people of Sans' world refer to the people of XTale as those "pale invaders".
• Despair Event Horizon:
  • Cross when he realized that Ink can't return X-Tale back to the way it was before.
  • Underswap Papyrus after Nightmare deliberately uses reverse psychology on him to destroy his morale and make him an easy kill for X-Event Chara.
  • Sans himself after 0.4, to the point that in 0.5 he flat out calls the multiverse hell, and later he's just sitting eating fries while the city is literally burning. He just doesn't care anymore.
• Didn't Think This Through: Despite everything, Ink still holds to the belief that XGaster will fix the multiverse even though there's ample evidence to the opposite that Ink is privy to. Cross calls him out on this after Ink says XGaster won't erase the alternate timelines, because he has done so ten times already.
• Disowned Sibling: XPapyrus declares in 0.8 part 1 that Cross is not his brother and that he would never be brothers with a killer.
• Do Not Call Me "Paul": "Cross" was originally just a nickname XFrisk gave to him, but after XGaster started using it and their manipulations were revealed, Cross demanded from the others in his verse to call him "Sans". Averted after his universe gets destroyed, as he introduces himself as Cross, most likely for convenience (there are a lot of doppelgangers running around) as he doesn't appear to like it much. By the time of Underverse 0.8 part 1 he does an 180 turn and demands from XPapyrus not to call him Sans, and that his name is Cross.
• Does This Remind You of Anything?: The scene where Cross yells at XPapyrus his name Cross comes off a lot like a trans person demanding from their family to stop dead naming them. Later posts from Jakei reveal this is completely intentional.
• Downer Ending: The XTale animation and prequel comic end with Cross himself having destroyed his world in his attempt to become the X-Event, not knowing that as a monster, he cannot use the OVERWRITE button.
• Early-Installment Weirdness:
  • In 0.0, X-Event Chara holds Ink up by making his soul blue. The creator of Ink stated that he has no soul. So in the Season One movie, it's instead the half of XGaster's soul he holds on to.
  • Nightmare went through several font changes, first Chiller Std in the original 0.1 Part 5 and 6, then Haunt AOE starting in 0.3 Part 1 and eventually the revamped version of 0.1, then finally to Sakkal Majalla Bold starting in 0.4 and in the Underverse Season 1 Movie.
• Emotion Eater:
  • In order to be able to feel at all, Ink drinks vials containing reflections of the feelings of the AU creators. He gets a massive complex over the possibility of those feelings running out on day. Notably, even as he runs out of paints he refuses to drink the blue vial, and he has also never experienced pain before until he drinks a vial made by XGaster.
  • As per their source material, Dream and Nightmare become more powerful depending on the presence of people's emotions in the area, with Dream becoming more powerful with positive ones and Nightmare with negative ones. This makes them both The Empath. Dream is almost always at a disadvantage in terms of power because he deliberately goes to miserable worlds to try and save them. Nightmare gives an "As Long as There Is Evil" speech based on this trope, telling Cross that he'll be always present whenever he feels guilt or doubt.
• Eviler than Thou:
  • Many of the other antagonists pull this on poor Cross.
  • X-Event Chara becomes a victim of this as well in 0.4.
• Extreme Omnivore: XMettaton can and will eat anything, including souls. In fact, souls are his favourite snack.
• Failure Hero: An interesting case with the entire squad around Ink. While they do succeed in their original goal (Stopping Cross and getting Classic Sans' soul back together), they suffer way more losses than they achieve victories along the way, getting downright curb-stomped several times and only surviving some encounters through sheer dumb luck or because whoever beat them wants to use them for something. It only gets worse once their opponent becomes X-event Chara and later on his psychopathic father XGaster. Both highly unstable Reality Warpers. At the end of season 1, Underswap- and Underfell-Sans have been killed, Ink is revealed to have been Evil All Along, meaning he never intended to succeed to begin with and Classic Sans is left a Shell-Shocked Veteran so traumatized by the deaths of his friends and Ink's betrayal that he just gives up entirely and is ready to let XGaster win.
• Fighting Across Time and Space: In episode 0.4, the final battle between Ink and XGaster, Nightmare and his gang, XChara, Error, and Sans and his allies, begins at Outertale, before Ink teleports them all to the Doodlesphere, and then they also take a brief detour to the Anti-Void. Eventually they ones who survive are left in a black space, which is unclear where it's supposed to be.
• Five-Second Foreshadowing: Geno tells Cross that there are many ways to break out of isolation and that he should be careful which version of himself does this. Cross and Ink are attacked by Fatal Error immediately afterwards.
• Force Feeding: Fresh forcibly feeds Ink the paint vial made by XGaster that was intended for him. Ink is shocked by the result, because the vial is made of pain, which is something he has never felt before and he had no idea this was what drove XGasster's creations.
• Foregone Conclusion: The prequel comic tells the story of X-Tale and Cross' origin, so by the end, X-Tale will somehow be corrupted, leaving the universe an empty void with only Cross and X-Event Chara. Turns out, it was Cross himself who caused it because he had no idea that he would be unable to use the OVERWRITE button as a monster, and also killed X-Event Frisk, thus rendering his efforts All for Nothing.
• Foreshadowing:
  • In the prequel comic, after XGaster RESETS the timeline to the day of Undyne's surprise test, XTale Papyrus seems a lot more nervous this time around. This is because he is among the people who have received their memories back and he is in on the plan to eliminate Cross and overthrow XGaster.
  • In 0.3 Part 1 Ink offhandedly refers to Classic and Fell as "weird clones that will die soon". Sure enough, Fell and Swap, the actual "weird clones", are killed by being Impaled with Extreme Prejudice at the end of 0.4.
  • In 0.3 Part 2, Dream briefly wonders why he can't feel any emotions coming from Ink. In 0.4 it is revealed that Ink is actually an Empty Shell, with no feelings of his own.
  • Throughout Season 1, there are various hints that Sans and his Pacifist Timeline have something very wrong with them, from Frisk talking about a promise they made in 0.1, to him having memories about a Genocide Run, to his internal comment about becoming the owner of a world by accident in 0.4. The Season 2 Preview reveals that Sans timeline broke after he killed Frisk/Chara during a Genocide Run, making him the new owner of the world as a consequence.
  • In XTRA SCENE 2, Fresh mentions that Ink promised him something nice out of his game. In addition, the artwork for Fresh's theme features a purple gift box. That box shows up in 0.5, made by XGaster at Ink's request.
• Freeze-Frame Bonus:
  • A lot of them, especially in 0.3 Part 2. Most of them are attributed to XGaster.
  • A single frame in XTALE X - CROSS shows a vision of Ink watching as XGaster falls into darkness.
  • Looking closely at X-Muffet's and X-Mettaton's dialogue boxes during the fight scene in 0.5 reveals a second string of dialogue underneath the more visible one, saying "Help us" and "Forgive me" respectively.
• Gag Censor: Whenever someone swears, Fresh switches out the word with a punny Totally Radical version, complete with rainbow text. Underfell Sans learns this the hard way.
• Gambit Pileup: The conflicts between Cross, X-Event Chara, Error, Nightmare, Ink, and XGaster are what kick off the main plot.
• He Who Fights Monsters:
  • X-Event Chara and X-Event Frisk started out as purely heroic characters who disapproved of their father's abysmal treatment of their friends in the XTALE timelines and made it their goal to stop him, so that everyone could live free of his influence. His constant torture and mistreatment slowly whittled away what sanity and altruism they had, leading to their sincere desire to free their friends to become a need to make sure that XGaster dies so that they can take control.
  • Cross was a Royal Guard in his timeline and one of X-Event Frisk's best friends. When X-Event Frisk tried to pull him into his and X-Event Chara's Thanatos Gambit, Cross is shocked and hurt but still tries to reason with his friend. X-Event Frisk thanks him by fatally injuring him with the OVERWRITE button and telling Cross that he will understand in the next world. Cross doesn't really take it well. He ends up inadvertently saving XGaster because for all he knows the X-Event experiment are worse, killing all of his friends and causing a Genocide from the Inside when he takes X-Event Frisk's soul. It all just goes further downhill from there...
• Heel–Face Revolving Door: What Cross' situation boils down to. He is pretty anti-XGaster through most of the series, ends up joining Nightmare (or rather, being forced to join), then Dream rescues him, and finally he joins XGaster on his own accord because he "needs to see [the people from his timeline] again".
• Heroic BSoD:
  • Ink after the effects of his vials begin to wear off. It doesn't matter at all, as one of Ink's hidden goals is to resurrect his friend XGaster, having promised to give him better feelings than the emotion vials themselves.
  • Underswap Papyrus after Nightmare makes him hit the Despair Event Horizon.
• Heroic Wannabe: Ink.
• Hijacked by Ganon: The role of the primary antagonist has been occasionally shifted for the most part. Cross is shafted over in 0.3 Part 1 by X-Event Chara, who also gets this by XGaster and Ink in 0.4.
• Heroic Self-Deprecation: In 0.7 Part 2, Cross says that his skills as a Royal Guard are nowhere near as impressive as those of say, Undyne's counterparts across the multiverse. Sure, Cross isn't on the multiverse heavy hitter list without X-Event Chara around, but he did solo literally everyone from his own timeline simultaneously while dying so his fighting skills are a lot more impressive than he makes it sound.
• Hope Spot:
  • In 0.3 Part 1, Sans finally gets his soul back from Cross with the help of Underfell Sans and Underswap Papyrus and Cross is knocked out cold. Unfortunately this causes X-Event Chara to awaken and snatch Underswap Chara's Soul, who was standing a little too close. X-Event Chara proceeds to go berserk and banishes Fell and Classic to XTale, along with almost everyone else from Underswap. He then uses his OVERWRITE-button to take control of the remaining Underswap characters and announces with a smile on his face that he will torture them now, in order to pay Nightmare back with their suffering.
  • In 0.3 Part 2, after returning to Underswap with the help of Dream, Classic Sans manages to fatally wound X-Event Chara, causing a part of the stolen soul to return to Underswap Chara and for a while it seems like there's still hope for the heroes to win. But then Nightmare gets impatient and stabs Underswap Chara, destroying their soul and flees with X-Event Chara, who ominously tells Sans to spent his remaining days remembering what he once lived. After that, the Underswap universe falls apart completely, forcing the heroes to flee and leave Underswap Papyrus and a dying Underswap Chara behind.
  • Earlier in 0.3 Part 2, it looks for a second that Chara might surrender and leave, but Nightmare goads him into attacking again.
• Hypocrite:
  • Plenty from XGaster.
    • He says at multiple points that his wants XTale to be unique and not rehash other realities. Yet he literally copies Underswap to the point that Cross notices, and starts old-fashioned Genocide timelines to make things more interesting.
    • Cross calls him out on this when he decides to rescue him from Nightmare, even though he told him earlier that he won't interfere with Cross' actions. Nonetheless, that saved Cross' life.
  • When XChara calls out XGaster for restoring the memories of Frisk's previous runs to the residents of Undertale, XGaster calls him a hypocrite and reminds him XChara did the exact same thing before.
  • Cross calls out Ink for accusing him of acting like XGaster while Ink was helping XGaster all along.
  • XPapyrus is correct when he calls Cross a murderer, but considering how he tried to murder Cross first, while XTale's Monster Kid was right in his way, and he did that before he was Brainwashed and Crazy, he doesn't exactly have the higher moral ground here. He even flings this accusation while trying to choke someone else.
• Hypocritical Humor: Cross tells Chara "the adults are talking" when he tries to interrupt an argument with XGaster. Chara responds by saying he is an adult and flipping the bird. Really mature.
• I Choose to Stay: Underswap Papyrus chooses to stay behind with Underswap Chara as they are dying while telling his brother to leave so that he may live. It's implied that he did this because he didn't trust Ink and didn't want to be used by him.
• I'm Cold... So Cold...: Nightmare mocks Underswap Papyrus by saying this as he rushes in to stop his brother from unintentionally killing Underswap Chara.
• In-Series Nickname:
  • "Cross" starts out as one, given to XSans by X-Event Frisk. Cross eventually takes it as his real name.
  • CORE Frisk calls XGaster "Mr. Curious Man".
• Inconsistent Episode Lengths: The first animation was barely a couple of minutes long, followed by other shorts of similar length before being incorporated into the first episode, which lasts about 20 minutes. The rest episodes of Underverse have a 20+ minutes length (though not uniform), and the extras (interludes and Xtra Scenes) all over the place in terms of length. Same goes for the prequel series Xtale, with episode lengths that range from a couple of minutes to half an hour.
• It Amused Me: XGaster's stated reason for not brainwashing XChara. He prefers to see him suffer.
• It's the Only Way to Be Sure: XTale Mettaton straight-up massacres the Underfell cast except Underfell Sans in preparation of its own quarantine.
• Laser-Guided Amnesia: It's revealed that XGaster can alter memories without anyone being aware, because the characters from Epictale clearly remember meeting Cross before, while he doesn't remember anything.
• Let's You and Him Fight: In 0.8 Part 1, XGaster says the ideal outcome for the XPapyrus vs Cross and Papyrus fight is if they all die in it.
• Lodged Blade Removal: Underfell Sans attempts to kill Cross by impaling him with a Ballistic Bone. Cross just laughs and pulls it out before continuing the fight, even though the bone was covered in his blood.
• Lotus-Eater Machine: In 0.8 part 1 XToriel creates a field that's seemingly paradise, just a peaceful flower field, where everyone has forgotten the painful memories of their past. Some even revert back to children. It's noted that the effect is stronger the closest they are to her, but it's possible to break through the brainwashing, with some characters being unaffected from the get-go. Cross thinks she is a full-blown Reality Warper, seeing how the illusion that took over the landscape holds even without the memory alteration. XToriel herself thinks that living in the illusion of a happy past is better than the present.
• The Man Behind the Man: XGaster, being the one responsible for starting his experiment on XTale Chara and XTale Frisk.
• Medium Blending: Fresh's bombs are blatantly photoshopped Furbies. Like, actual photographs of the things.
• Mega Crossover: Between several different Undertale AUs. Those include Underfell, Underswap, Outertale, Dreamtale, CORETale, Inktale and Killer Sans, the series-original XTale, along with the original Undertale (or so it seems at first) and quite possibly Errortale (it's unknown if the Error that appears is the same as the one in the original). Season 2 adds even more AUs.
• Mind-Control Eyes:
  • Whenever X-Event Chara/Cross takes control of another person, a giant white fuzzed out X appears on their face, indicating they are under their control. This is purple in X-Tale X, and red in Underverse.
  • Whenever XGaster uses the Overwrite-button to take control of a character, their irises become purple crosshairs.
  • Possibly invoked by XGaster. Most of the X-Tale characters that show up with him at the end of 0.4 have a purple crosshair-like object in their eyes, possibly indicating that they are no longer themselves and are just puppets within XGaster's "game". It's confirmed in 0.5.
• Mirror Boss:
  • Considering that the cast of the first season is literally just Sans, every single fight is this. However, they only ones who truly fight the same as Undertale Sans and Underfell Sans, with the rest mixing up their styles or having completely different magic.
  • 0.5 sees Muffet and Mettaton vs. their XTale counterparts. In this case, their powers and fighting styles have practically nothing in common.
• Moment Killer: Ink has a habit of throwing up or making out out-of-place, weird comments in tense situations.
• The Multiverse: The premise is that one timeline is destroyed and Cross starts stealing from the other universes, with Ink and Sans trying to stop him.
• Nice Job Breaking It, Hero!:
  • Underswap Chara gets too close to X-Event Chara, which gives him an opening to take 95% of their soul, allowing him to be revived and start causing trouble for the heroes.
  • Cross' attempt to become the X-Event and make a better world is what directly caused his world to become irreparable in the first place.
  • XTale Undyne's refusal to outright kill XGaster during their confrontation in timeline V is what led her and XTale Chara to fail in the first place and what allows XGaster to take half of Chara's determination soul.
• Nightmare Face: X-Event Chara and later on XGaster are very good at pulling this.
  • Ink does one as well in Xtra Scene 2.
  • Flowey does this in OWNERS.
• No Antagonist: Even though there are quite a few candidates that could pass as the true antagonist, Jakei has explicitly stated that there is no real antagonist, thus many have different opinions on who's the bad guy in the story.
• Noodle Incident:
  • Combined with Hero of Another Story. Underswap Sans and Underswap Papyrus appear to be this. Not only they are already acquainted with Ink, but US Sans says that he knows there are alternate universes where they all suffer, and both Dream and CORE Frisk show familiarity with the two brothers. One can only wonder what happened between their initial meeting with Ink and Underverse 0.3.
  • Dream says that he and Ink used to work together but split apart due to "differences in opinion". It's unclear what exactly Dream means by that or what the exact circumstances behind the split were.
  • The XTale residents have met those of Epictale before, but XGaster deleted all of XTale's memories of those events because he thought they'd get in the way. Nobody elaborates on what exactly happened, but everyone treats Cross as a friend.
• "Not So Different" Remark: In 0.7 Part 2, Cross laments that he and Ink both hoped for a way to fix everything; Cross with OVERWRITE and by stealing codes to try to recreate Xtale and Ink by putting his faith in XGaster.
• Offscreen Moment of Awesome: In 0.8 Part 1, several battles are happening simultaneously so most of them are skipped in a certain degree. Papyrus' fight against his counterpart is skipped almost entirely, at least until Cross arives, and then it gets skipped again only to show a single shot of Cross blocking a strike from XPapyrus, with Papyrus' red scarf tangled on the scythe to show Papyrus barely avoided a lethal strike.
• Older Than They Look: X-Event Chara and X-Event Frisk look like 10 year olds, but they are actually 18. In truth, they are actually far older, as they've lived through multiple timelines.
• Painting the Medium: Just like the source material, all characters speak in their own fonts.
  • All non-skeleton characters use 8bitoperator.
  • The Sanses (including Cross and Dream for some reason) speak in Comic Sans. UT Sans and UF Sans switch to 8bitoperator when threatening people or are serious.
  • Cross and XChara switch to Chalkboard for the same thing.
  • The Gasters overlay Windings and Tahoma at once.
  • Fresh changes the colours of his speech bubble with every line.
  • Ink and Nightmare have switched fonts several times through the series.
• Paper Cutting:
  • This happens to Cross in XTale when X-Event Frisk slices his face with a knife while trying to kill him, leaving him with a scar.
  • It also happens in Underverse 0.4 when Error, while using his strings to snatch the vial containing half of XGaster's soul from Ink, attacks Ink by launching a bone at him and cuts his face.
  • In 0.6, during the Dream vs. Killer fight, Dream uses one of his blades to slice a small cut into Killer's left cheek.
• People Puppets:
  • Heavily implied to be the case with XAlphys, who while is incredibly loyal to XGaster, secretly disapproves of his actions. Basically confirmed in XTALE 5, where it's revealed that XGaster Overwrote her to act as his cold and loyal assistant.
  • In XTALE X, XFrisk and XChara tried to unsuccessfully use it as a suicide method; they would use Overwrite to force humans to attack Frisk, and they wouldn't remember attacking later.
  • In the first season of Underverse, Cross obtains the ability to control people by stabbing them with his Hack Knife. However, he can only do it with Chara's help.
  • In 0.3 part 2, X-Event Chara uses Overwrite to take control of Underswap Sans and Papyrus.
  • Error is capable of controlling people's bodies by wrapping their souls with his strings, clearly evoking the "puppet" part of this trope.
  • In 0.5, XGaster forces his will on every single XTale cast member (except Cross and XChara), leaving them to cry for help but unable to express their words. His control is so good that he can speak through them.
  • In 0.6, it is revealed that XGaster could take control of Cross at any time. He does so to fight Killer and protect Dream, although his reasoning is largely unknown at this point.
• Pet the Dog: For whatever reason, XGaster decided to save Cross' life from Nightmare. When asked, he says that "emotions distract him".
• Poor Communication Kills: XTale Toriel fights Undertale Toriel, after Undertale Toriel destroys her counterpart's illusion.
  XTale Toriel: I don't want tears, I don't want sadness. I don't want any of you to die in vain. WHY DON'T YOU UNDERSTAND WHAT I'M TRYING TO DO FOR YOU...!? THAT WORLD YOU COME FROM IS DROWNING IN PAIN...WE CAN STAY FOREVER IN THE MOMENT WHEN WE WERE HAPPY AND UNAWARE.
  Toriel: I've carried regrets, but I can't stay stuck there... Sorrow and Joy coexist. That's what the real world is made of!!
  • XTale is an artificially constructed world, which, when exposed to sorrow, was destroyed and rewritten repeatedly. XTale Toriel is attempting to save Undertale Toriel from her fate, but does not understand Undertale, which is not artificially constructed in the same way. Both of them are trying to save the other from what they think is a distortion of reality (XTale Toriel is Brainwashed and Crazy, but still acting on best intentions). Their inability to communicate their real problems keeps them both fighting, and XTale Asgore breaks up the fight, and their chance at understand each other, by killing Undertale Toriel.
• The Promise: At the end of XTale I, Asriel promises XTale Chara and Frisk that "We will play and laugh together just like we did in our childhood." This is brought up again in Underverse 0.8, Part 1, where XTale Asriel tells XTale Chara "Let's keep laughing and playing like we promised!" in XToriel's illusion.
• "Rashomon"-Style: The destruction of X-Tale is told through two stories: first is the prequel comic that focuses on Cross's point of view, while XTALE X narrates the same events from XGaster's point of view. Which is interesting because we see from Cross's POV that at that point in time he doesn't actually consider XGaster a priority compared to XFrisk and XChara.
• Reality Warper:
  • What anyone who has at least half of XGaster's soul becomes as long as they are human. With OVERWRITE, they have the ability to do pretty much anything.
  • It appears that the XTale cast after XGaster revives them have a localized version of reality alteration. It happens to Cross while he's in the Omega Timeline, and later XToriel creates a Lotus-Eater Machine version of it.
• Really 700 Years Old:
  • Everyone from X Tale, due to XGaster's meddling.
  • Cross calls Dream "kid". Dream responds he's 500 years older than him.
• Recursive Fanfiction: Underverse is a crossover between several other popular Undertale fanworks. In turn, it has inspired several other fanworks, with some notable ones being Abysstale and Dreamswap; and that's without counting the countless smaller fics that feature Cross in some capacity.
• Sadist:
  • X-Event Chara takes delight in torturing the Underswap cast in 0.3 Part 2. Underswap Sans can't understand why he takes joy in hurting them like that.
  • XGaster develops a liking for tragic stories and indulges in it by putting his "characters" through as much suffering as possible. In 0.5 he even tells XChara that he only keeps him around for his amusement.
• Screw the Rules, They Broke Them First!: Error and Ink made a truce before the series that neither of them would create or destroy AUs. When Error believes that Ink’s agreement with XGaster is violating the truce, he decides to destroy the entire doodle sphere right in front of Ink and the other characters.
• Screw This, I'm Outta Here!: Error's reaction to Fresh Ink (and the triggering of ALL his phobias that follows) is basically to Rage Quit the X-Event entirely.
• "Shaggy Dog" Story:
  • The X-Tale shorts tell the story of how XGaster became the power-hungry Control Freak he is. X-Frisk and X-Chara make multiple attempts to stop him, but they always end up losing to his Reality Warper-powers. When it finally looks like they have the upper hand on him in the finale, Cross, whom they turned against them with their manipulative nature, throws a wrench into their plans, throws XGaster out of their reach and claims X-Frisk's soul for himself.
  • The entirety of season 1. Ink gathers a group of Sanses to stop Cross and X-Chara from destroying the multiverse. In 0.3, part 1, they manage to stop Cross, but then X-Chara takes over as the Big Bad. Even worse, in 0.4 it's revealed that Ink is secretly working for XGaster, the actual Big Bad. The multiverse ends up destroyed in the ensuing scuffle and Underswap- and Underfell-Sans are killed. XGaster reclaims the missing half of his soul and prepares to conquer the main universe.
• Shared Life-Meter: What happens when two beings have different parts of the same soul. Sans and Underswap Chara find this out the hard way.
• Sharing a Body:
  • From timeline 8 onwards, XGaster forced XChara into XFrisk's body. Surprisingly, the two don't find the situation too bad.
  • In timeline 10, Cross forces XChara into his body in hopes of obtaining the power to Overwrite. Cross and XChara keep fighting for control until the latter steals Underswap Chara's soul, and the two finally separate when XGaster kills them and revives them in different bodies.
  • OWNERS heavily implies that normal Frisk and Chara also share their body, something that is confirmed in 0.5.
• Significant Wardrobe Shift: While many characters change outfits due to their clothes getting destroyed in fights, Sans is a standout. Though his jacket was also destroyed in a fight, the outfit switch that is forced on him by his friends comes after The Reveal that he's the Owner of his timeline, thus marking this version of Sans as a different person from his canon counterpart.
• Skewed Priorities:
  • After his talk with Geno, Cross starts pondering on the nature of Alternate Multiverses and if they really are the best version of themselves... while stranded in a white void by an unknown force. Ink facepalms before yelling that they have enough problems already and this ISN'T the time for existential questions.
  • Papyrus is more annoyed about his car getting wrecked than the literal end of the world.
• Sympathy for the Devil:
  • Quite a few heroic characters express sympathy towards XGaster, particularly when he's questioning his worth compared to other versions of himself. CORE Frisk and Dream assure him that all existance is equally precious and they're not inherently superior and inferior. CORE Frisk even takes the time to make XGaster comfortable and tells him they want to keep in contact with him in case he ever wants to talk.
  • Cross wishes good luck to Killer for dealing with Nightmare in quite the sincere fashion.
• Take That, Audience!:
  • In XTALE 0, Ink breaks the fourth wall to directly address the audience and the Undertale fandom in general; particularly, all the creators who abandoned the fandom and deleted their works over the years because they thought their creations weren't good enough. He says that it is essentially our fault that he took the decisions he did, as he does not want to be forgotten. He essentially presents XGaster as a replacement for us.
  • In a more indirect manner, XGaster is a Deconstruction of the perfectionist author. It is outright stated that he is never satisfied with his own ideas, and keeps redoing his work over and over and over again, accepting nothing less than some unobtainable concept of perfection. Many times he even relies on plagiarism and idea-stealing; for example, for Timeline 3 he literally copied Underswap. His behavior overall mirrors many, many creators of all genres and art forms, and many viewers have admitted that they see their own behavior reflected in XGaster. However, unlike us, XGaster has to live with his creations, and they are NOT happy to be continuously discarded.
• Taking the Bullet:
  • Ink taking the brunt of Errors' attack to protect Cross in the 0.1 flashback.
  • Sans teleports in front of Underswap Papyrus in order to save his life. Luckily, the deluxe ketchup bottle he got from Frisk in Underverse 0.1 saves him.
• "The Reason You Suck" Speech: There are a lot of those.
  • Several characters over the course of the series call out XGaster on his perfectionism, insecurities, and Can't Take Criticism attitude, from XFrisk and XChara to the main version of Gaster to even Killer.
  • Fresh delivers one to Ink in 0.7 Part 1, calling him out on how he only cares for himself, thinks that things that apply to him also apply to other people, how he needs external validation to feel a void inside, and he cares too much about living in the moment that he can't think about anything else.
  • In 0.7 Part 2 Geno delivers a much shorter version to Ink helped destroy the world over what he thought would be "a silly little game". When Ink tries to defend himself, Cross doubles down by calling out Ink on his hypocricy for accusing Cross to be like XGaster while helping XGaster.
• This Cannot Be!: X-Event Chara, as he realizes that his efforts were All for Nothing, yells "It's Not Fair " before he (temporarily) dies.
• Trailers Always Spoil: Some of the reference sheets for the XTale characters can end up spoiling some parts of Underverse Season 2. For instance, in Cross' reference sheet, where it goes over his eyes, one of them shows him being under control by XGaster.
• Wham Line:
  • One from X-Event Frisk in the prequel comic, which marks the point where his true character comes to light.
    X-Event Frisk: Sans...I've been forcing you to kill me.
  • "They are not my friends." Said by Ink in 0.4 about the other Sanses, revealing that he was Evil All Along.
• Wham Shot: Two in quick succession in 0.4. When Underfell Asgore attacks XTale Alphys, there is a shot of her right purple eye and Underfell Asgore looking surprised before it cuts back to XTale Mettaton, who is effortlessly blocking the attack.
• What the Hell Are You?: Fell Sans' reaction word for word when Cross survives being hit by his surprise attack in 0.2.
• What the Hell, Hero?: Everyone to Ink once they realized he's been attempting a revival of XGaster.
• Wingdinglish: XGaster and normal Gaster always speak with a layer of Windings beneath their speech. XAlphys also writes all the entries in Windings, and at one point she and XGaster talk in it. Apparently, it sounds different enough from regular English that bystanders cannot understand it.
• Would Hurt a Child:
  • Underswap Sans when he tries to fight X-Event Chara. Since he has absorbed 95% of Underswap Chara's soul, his attacks hurt the both of them.
  • Basically all the Sanses and X-Event Chara, thought it's kinda Justified as well as Subverted, since X-Event Chara is Really 700 Years Old and an Ax-Crazy Reality Warper.
  • Nightmare at the end of 0.3 part 2 as he stabs Underswap Chara.
• "X" Makes Anything Cool: X-Tale and all of its characters associated with it.
  • In 0.2 Part 2, Cross cuts apart Ink's wall with a X-slice.
  • When half of Sans's soul is stolen, his remaining half is instantly marked with a red X. The same goes with Underfell Sans under Cross's control and the majority of the Underswap cast after X-Event Chara steals all of them for Nightmare's gamble.
  • Interestingly enough, Cross is the 10th character in the X-Tale cast when referring to the timeline entries. Since the entries are referred to by their Roman numerals, Cross's placement makes logical sense.
  • Lampshaded when Ink notes that XGaster really likes the letter X.
• Year Outside, Hour Inside: 0.5 reveals that in the main universe, only a few hours have passed between Sans' departure and return.
• You Have GOT to Be Kidding Me!: Cross reaction when he finds out his ride to the Anti-Void is Fresh of all people.
• You Have Outlived Your Usefulness: In 0.8 Part 1, Ink confronts XGaster and tries to convince him to stop his plans, declaring that he will protect everything from him including XGaster himself. XGaster says he doesn't need Ink anymore and sends XMettaton to attack him and Sans. XMettaton swings at them with his sword but it isn't seen if the attack lands and either of them are hit.

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